Environmental advocacy group CSE India said experts witnessed the worst incidences of smog in 17 years on November 2, with the government blaming the pollution largely on fireworks being set off during the Hindu festival of lights.

“This demands emergency response to protect the vulnerable - those who are suffering from respiratory and heart diseases… The government should aggressively inform all and advise them to stay indoors and avoid outdoor exercises,” Roychowdhury said.

“At the same time, it should roll out stringent winter pollution control for all sources along with emergency action."

CSE India say their analysis shows that post-Diwali pollution has been higher than during the religious festival.

Daily updates provided by the nation’s state meteorological department reveal air quality in Delhi has been severely poor since November, with reports that a number of schools had to be shut as a result.

Pollution has ranged from 300 to 500 on the Air Quality Index in the past week, a level which according to US Environmental Protection Agency standards is “hazardous”or at the least “very unhealthy” to humans.

“Hazardous AQI greater than 300,” the EPA website states, “would trigger health warnings of emergency conditions. The entire population is more like to be affected.”